1. Field of the Invention
The present invention pertains to the field of hydraulic locking devices and more specifically is an improved, more easily adjustable cable control mechanism for releasing a hydraulic locking device by an operator from a remote location.
2. State of the Prior Art
Hydraulic locking devices have been widely used for controlling the spacing between two members. In one exemplary application, the hydraulic locking device is used for controlling the inclination of a tiltable back rest of a reclining seat in aircraft and other vehicles. This use of the device is described in U.S. Pat. No. 2,522,246 for RECLINING CHAIR, issued to Armstrong Sept. 12, 1950.
Typically such hydraulic locking devices include a hydraulic cylinder connected to one of the members, a hollow piston rod extending through one end of the hydraulic cylinder and connected to the other of the two members, and an operating rod extending coaxially within the hollow piston rod and protruding beyond the exposed end of the piston rod, and operative when pushed into the piston rod to a release position to release the hydraulic locking device so it can be reset to alter the separation between the two members.
Contemporary locking devices are disclosed in U.S. Pat. No. 3,760,911 for HYDRAULIC LOCKING DEVICE, issued to Porter et al Sept. 25, 1973 and in U.S. Pat. No. 3,860,098 for HYDRAULIC LOCKING DEVICE, issued to Porter et al Jan. 14, 1975. The devices described in these patents are sold under the name HYDROLOK, a registered trademark of the P. L. Porter Company of Woodland Hills, Calif., to whom the aforementioned patents have been assigned. The subject matter disclosed in the above patents is hereby incorporated into the present disclosure by this reference.
A hydraulic control assembly is disclosed in U.S. Pat. No. 3,553,967 for HYDRAULIC CONTROL ASSEMBLY, issued to Porter et al Jan. 12, 1971 and in U.S. Pat. No. Re. 28,030 for HYDRAULIC CONTROL ASSEMBLY to Porter et al, issued June 4, 1974. The hydraulic control assembly disclosed in these patents includes a push button operable by a passenger in a vehicle to release the hydraulic locking device so that he can adjust the tilt of the back of his seat. The push button includes a plunger which presses against a diaphragm to cause a hydraulic pressure, which pressure is then transmitted through a tube to a movable wall or diaphragm which controls the release of the locking device. In contrast to the hydraulic control assembly, the present invention relates to a mechanical control assembly in which the forces are transmitted by a cable instead of through a tube filled with hydraulic fluid. The present invention thus relates to a control mechanism which attaches to the locking device to permit an operator to trip the release mechanism of the hydraulic locking device from a remote and more comfortable position. The hydraulic locking device in itself is not the subject of the present invention, but only the control mechanism.
Because the hydraulic locking devices are frequently used to control the tilt of the back of the seat in a vehicle, the hydraulic locking devices are normally positioned under the seat to prevent tampering and for aesthetic reasons. Accordingly, the control mechanism must be rugged and reliable, easy to mount to the hydraulic locking device, and easy to adjust. It is desirable that the placement and adjustment of the control mechanism should be accomplished without removing the hydraulic locking device from the seat and without removing the seat from service for more than a minimal amount of time. The control mechanisms of the prior art suffered from various shortcomings, particularly in that the manner of attachment of the mechanism to the hydraulic locking device required tools which were difficult to use in the cramped quarters and poor illumination typical of the environment where the devices are used. In addition it was difficult to adjust the end points of the stroke of the cable; i.e., to trim the cable to the proper length relative to the length of the conduit through the which the cable passes.
Applicant's copending patent application Ser. No. 157,356 and assigned to the same assignee as this application provides a partial solution to the shortcomings of the prior art. The control mechanism disclosed therein requires no tooling for attachment to the piston rod of the hydraulic locking device. The lever assembly is provided with a single slidable spring clip which serves the dual purpose of retaining the proximal end of the cable conduit to the lever assembly as well as securing the lever assembly to the exposed end of the piston rod. "The lever assembly" as used in the present specification refers to the portion of the control mechanism which is attached to the piston rod. The lever assembly is attached to the hydraulic locking device simply by inserting the tip of the piston rod through a hole in the lever assembly, and sliding the spring clip into engagement with a circumferential groove formed near the end of the piston rod.
The lever assembly is actuated by a cable which is drawn through a conduit under control of an operator. The operator is provided with a push button assembly which includes a crank which draws the cable through the conduit when a push button is pressed. The proximal end of the cable engages the lever assembly and the distal end of the cable engages the crank. The distal end is provided with a metallic ball or bead threaded or swaged to the cable and which may be also crimped in place. The larger size of the ball prevents the distal end from being pulled through the socket in the crank upon which it bears, thereby securing the cable to the crank.
When the cable is drawn through the conduit in response to the remote push button control unit being pressed by an operator, the output lever is pivoted relative to the mounting base and in so doing, the output lever pushes the operating rod into the piston rod releasing the hydraulic locking device. A compression spring such as a helical spring positioned between the output lever and mounting base returns the output lever to its original position when the push button is released. The proximal end of the control cable was provided with a second, proximal metallic ball or bead affixed to the cable for engaging the output lever. The effective length of the control cable was therefore determined by the distance between the two balls measured along the cable. The placement of the proximal ball was relatively critical, even allowing for the modest cable length adjustment capabilities provided in the lever assembly. Further, the proximal end of the conduit was affixed to the lever assembly by means of a washer and a snap ring and a threaded collar was provided for adjusting the length of the conduit relative to the cable length measured between the proximal and distal balls. These considerations made it desirable to attach the cable and conduit to the output lever assembly at the factory, so that the control mechanism was supplied to the installer as a unit including the lever assembly and the push button unit interconnected by the control cable and conduit. In the cramped environments where these devices are typically installed adjustment of the cable length by means of previously used threaded collars was found to be inconvenient and difficult. It is highly advantageous to remove broken or damaged stranded cable from the conduit without removal of the conduit which extends through difficult routing in the seat arm and seat bottom with cast or swaged balls on both ends of the cable, removal and reinsertion of replacement cable is impossible. A means to eliminate the adjustment collar and clamp A cable without precision fitting is desirable. The range of adjustment to the cable length possible with a threaded collar is limited by the length of the collar itself. It was necessary therefore to make a fairly close initial approximation of the required cable length when the proximal and distal balls were affixed to the cable. The threaded collar could then be used to make the final adjustments.